The present invention relates to enhancing the quality of printing images.
In the field of printing technologies, there is a continuing need to provide the ability to generate the appearance of high-resolution printing on printers with lower resolution than would otherwise be required. For example, antialiasing is a common technique used to provide the appearance of high-resolution printing.
In particular, with antialiasing, the appearance of text and graphics is improved by smoothing the xe2x80x9cstepsxe2x80x9d that would otherwise appear as jagged edges in the diagonal lines of the text and images. More specifically, printed text and images are made up of thousands of tiny dots (picture elements), which when joined together create images and/or text. With antialiasing, the picture elements (pels) that would otherwise look like a step along the edge of a diagonal line, are printed at partial exposure levels in order to smooth out the step.
An additional technique for smoothing the steps of a diagonal line involves changing the actual color of white pixels that are adjacent to black pixels along the edge of a diagonal line. Specifically, the data representing the color of the white pixels is changed to alter the color of the white pixel to become more of a gray color. Therefore, a blended, smooth appearance between black pixels along a diagonal edge is generated.
The techniques of antialiasing and altering the color of white colored pels however, is typically more beneficial for text rather than images because while text typically relies on the outline of the characters, images rely on areas of gray to show shape, texture and shadow. As a result, if the actual color of white pels are altered to generate smooth outlines, areas of the printed image may become distorted from their binary representations.
In addition, as printing technologies continue to evolve, more dots per inch (dpi) are printed. By printing more dots per inch, the quality of printing may be improved. However, new problems are also presented by the dpi. For example, in conventional printers, black pels are typically printed more bold than their intended size (i.e., they are printed larger compared to their binary representations). As a result, areas of a printed image may appear darker than the true image as represented by the bit map. Moreover, with the increased dpi the over boldness of the black pels is very apparent, especially in images, which rely heavily on specific areas of grey to show shape, texture and shadows.
Therefore, a need exist in the prior art to provide an improved technique for controlling the over boldness of printed images.
The present invention provides a printing device that includes a first unit to receive data representing a first center pel and a set of neighboring pels. The printing device further includes a second unit that compares the first center pel and the set of neighboring pels to a set of pel patterns. In one embodiment of the invention, the pel patterns only have a center pel of a first color selected from at least two separate colors. In one embodiment, the pel patterns only have black colored pels as the center pels. In response to a match between the first center pel, the set of neighboring pels, and a pel pattern, a printing size of the first center pel is modulated. In addition, in one embodiment of the present invention, each pel pattern has a corresponding laser power level.